Briley gave me the following address in OZ and said that the price should be the same as theirs (US$399.00):

Mialls/Briley Australia
(Briley Thinwall, Full services and parts)
59 Playne St Frankston, Victoria, Australia, 3199
Technical (03) 97831576
Orders (03) 97811668
Fax:(03) 97837887

I assume they can tell you what choke barrels to order to simplify the installation.